The invention relates to a round cutting tool for cutters comprising a metallic basic body having a chisel shank, and a chisel bit consisting of a hard metal body fixed to the front end of the basic body and having a substantially cone-shaped working section.
Round cutting tools are used, e.g., for crushing and removing rock in mining and to remove worn road surfaces. The rotating chisel wheel of a cutter is provided with a number of chisel holders to rotatably support therein the shanks of the round cutting tools. As the chisel wheel is rotated, the individual round cutting tools successively engage the material to be removed which is frequently very hard and/or tough. As a result, the round cutting tools are exposed to high dynamic stresses and the chisel bits suffer form strong wear.
The chisel bit of a round cutting tool consists of a hard metal body whose working section forms a cone being round at the point and having a taper angle between about 30.degree. to 90.degree.. It is the object of the cone of the hard metal body to cut and break open the material to be removed. With increasing wear, the taper angles become greater and greater, i.e., the cone size is reduced to a round head. As a consequence thereof, the cutting action of the chisel bit will become insufficient and finally ineffective. With an increasing wear of the round cutting tool, the energy consumption for the rotation of the chisel wheel will be higher and higher. During the service life of the round cutting tool, the required energy frequently is three to four times higher than at the beginning because the chisel bits do not grip any longer correctly, the material to be removed being rather displaced than cut open and crushed.
The higher the forces acting on the chisel, the higher the stress to which the chisel shanks and holders are exposed. Since the chisels are operating in a strongly contaminated environment, the penetration of dirt into the region between the chisel shaft and the bore of the chisel holder entails a high wear if the attacking forces are correspondingly intense.